RF-sealable pillow pouch

ABSTRACT

A thermoplastic multi-layer film with an even number of layers containing first and second outermost layers each containing ethylene-vinyl acetate copolymer having between 14 and 22 wt. % vinyl acetate, first and second inner layers each containing vinylidene chloride copolymer, and first and second contiguous layers separating first and second inner layers from each other, each layer containing ethylene-vinyl acetate copolymer.

BACKGROUND OF THE INVENTION

The present invention refers to an RF-sealable pillow pouch of athermoplastic material particularly suitable for packaging flowableproducts and to a method of packaging said product in a verticalform-fill-seal machine using an RF sealable, thermoplastic material.

Flowable products, such as powders, liquid and pasty materials, e.g.detergents, liquid soaps, household cleaning products, bleaches, etc.,are currently packaged in so called pillow pouches made of PVC. Thesepillow pouches are typically used as monodose packages or as refillcartridges that are opened and poured in a re-usable rigid or semi-rigidcontainer as desired.

The machine that makes and fills packages in a single operation iscalled a vertical form-fill-seal (VFFS) machine. Said machine formspouches from a web of flat flexible film while filling them with theproduct. The film is fed from a roll to a device that forms it into atube of a suitable diameter around the product filling tube. The twofilm edges are then sealed together, longitudinally, either with a lapseal or with a fin seal. As the tube moves down the machine, twohorizontal sealing bars come together to form a transverse seal whichbecomes the bottom of the pouch. At that point, a measured amount ofproduct is allowed to flow through the product filling tube and into thejust formed pouch. By the time filling is complete, the top of the pouchhas traveled down to the sealing bar location, where the bars once againmeet to simultaneously create the top seal and the bottom seal of thenext pouch above. Alternatively, it is also possible to manufacture thepillow pouches in two separate steps, where the first step is theproduction of the pouches by any conventional system and the second oneis the pouch filling In a vertical machine followed by the sealing ofthe pouch mouth.

Pillow pouches are characterized in that at least one of the transversesealing is a melt cut sealing. The melt cut sealing Is a sealing carriedout with heating while at the same time the film is pressed and cut. Thesealing bars are therefore equipped with a knie which cuts through theseal to separate the filled pouch from the machine. To give theappearance of a pillow, as the name does suggest, once the pouch isfilled with the metered volume of flowable product, generally of theliquid or pasty product, air or a suitable gas is injected before thetransverse sealing bars are pressed together.

Working with PVC at least the transverse sealing system in these VFFSmachines is based on dielectric heating or RF heating. In this systemhigh frequency electric current is passed through the film by thesealing bars. When the film contains polar molecules, as in the case ofPVC, these molecules oscillate under the influence of the current andthis molecular agitation is converted to heat sufficient to melt thefilm in the seal area.

The advantages of “pillow pouches” are obvious: reduced volume, reducedconsumption and waste of plastic material, lower cost, etc.

However the use of PVC, that up to now has been considered the polymerof choice for this application, presents many drawbacks.

First of all PVC has no gas-barrier and moisture-barriercharacteristics. Volatile components, e.g. perfumes, aromas, etc., caneasily escape through the packaging material, thus reducing the contentthereof in the packaged product and, when these components have anunpleasant smell, e. g. in case of bleaches, imparting said smell to thewhole package. Water also can evaporate through the PVC layer thusreducing the volume of the packaged product and increasing theconcentration of the non volatile components therein.

Secondly, PVC generally contains a high level of plasticizers. Saidplasticizers do easily migrate Into the packaged product with aconsequent package integrity problem. The mechanical properties of PVCfilms in fact are determined by the level of plasticizers: a decrease Inthe amount of plasticizers due to their migration into the packagedproduct will increase the stiffness and brittleness of PVC thus reducingits mechanical (puncture, abuse) resistance.

A third disadvantage of the use of thick PVC films is the amount ofchlorine containing polymer that needs to be disposed of.

PVC replacement in the manufacture of pillow pouches for the packagingof flowable products has been widely described in the patent literature.

Of interest is EP-B-477,025 that describes the use of a multilayer filmhaving a barrier layer of a thermoplastic material, preferably an LLDPEor a composite of a polyethylene layer and a polyamide or EVOH layer,and on at least one side thereof a layer of an RF-sealable polymer, e.g.EVA with a high VA content According to EP-B-77,025, the problem createdby the low RF-sensitivity of the thermoplastic barrier materials isovercome by the use of sealing layers of EVA with a high VA content anda low, controlled, content of additives, while the problem of stickingthat derives from the use of such a sealing layer is overcome by the useof structures with a matted surface. These structures do not containchlorine and have moisture barrier properties, however they do notovercome the other drawbacks connected with the use of PVC as forinstance the structures described In EP-B-477,025 do not haveodour-barrier properties or only to a limited extent While in factpolyethylene and polyamide have no or moderate odor barrier properties,EVOH is very sensitive to moisture and its odor barrier properties, thatare satisfactory under dry conditions, are drastically reduced afterexposure to a moistured environment. Furthermore, owing to the lowRF-sensitivity of these barrier materials, and depending on theirthickness, the seal strength of the RF-seal may sometimes beunsatisfactory in spite of the high VA content of the EVA sealing layer.Finally, with these structures an additional step in the filmmanufacturing process is required to provide the matted surface, whatadds an extra-cost to the film.

Also of Interest is EP-A-471,607 that describes RF-sealablethermoplastic films particularly suitable for packaging gas-emittingflowable products. Said films comprise a core polyolefin layer and EVAsealing layers and are characterized by an oxygen transmission rate(OTR) of at least about 600 cm³/m².d.atm. This high OTR is required,according to EP-A-471,607, because in packaging gas-emitting products,such as bleaches, a gas, typically oxygen, is evolved during storage andshould be allowed to be dissipated through the pouch wall to avoid thatpressure builds up into the pouch and the pouch seal breaks.

Also the structure described in EP-A-471,607 does not contain chlorineand has moisture barrier properties but it has no odor barrierproperties. Furthermore, also in this case, the presence of a thick corelayer of polyolefin material with a low RF sensitivity affects the RFsealability of the overall structure. It is probably due to the low sealstrength of the thus obtained RF-seal that such a high OTR is needed toavoid breaking of the seal.

It has now been found that It Is possible to solve the above problems ina satisfactory way by using, as PVC replacement in the manufacture ofsaid pillow pouches, a film comprising an RF-sealable outer layer ofethylene-vinyl acetate copolymer with from about 14 to about 28 wt. % ofVA and a layer of PVDC.

The use of such a film as a PVC replacement offers many advantages asthe RF-seal will have a good seal strength because the presence of aPVDC layer improves the sealability of the overall structure; it hasalso been found that the presence of a PVDC layer imparts to the pouchthe desired balance of stiffness and flexibility so that films 75-150 μmthick can be run in the commercial VFFS machines giving a betterperformance than conventional 200-250 μm thick PVC films, and thusdrastically reducing the amount of plastic material per package whichneeds to be disposed of after use; the amount of chlorine containingpolymer is highly reduced as the PVDC layer will be only few micronthick while PVC pouches generally require a 200-250 μm-thick sheetFurthermore, by suitably selecting the thickness and/or composition ofthe PVDC layer it is possible to “modulate” the gas- and odor-barrierproperties of the end structure to the desired extent.

SUMMARY OF THE INVENTION

In accordance with the present invention, there is provided a coextrudedthermoplastic multilayer barrier film with an even number of layers,comprising first and second outermost layers each comprisingethylene-vinyl acetate copolymer, first and second inner layers eachcomprising vinylidene chloride, and first and second contiguous layersseparating first and second inner layers from each other, each layercomprising ethylene-vinyl acetate copolymer. Preferably, the outermostlayers of ethylene-vinyl acetate have a vinyl acetate content between 14and 22 wt. %, and the contiguous layers of ethylene-vinyl acetate have avinyl acetate content from 22 to 28 wt. %. The barrier film is a layflattubular film having its interior layflat surfaces laminated together byself-welding.

As used herein, the term “homopolymer” is used with reference to apolymer resulting from the polymerization of a single monomer, i.e., apolymer consisting essentially of a single type of repeating unit.

As used herein, the term “copolymer” refers to polymers formed by thepolymerization reaction of at least two different monomers.

As used herein, the term “polymer” refers to both homo-polymers andco-polymers as defined above.

As used herein the term “ethylene homopolymers” identifies polymersconsisting essentially of an ethylene repeating unit

As used herein, the phrase “ethylene α-olefin copolymer”, and“ethyieneolα-olefin copolymer”, refer to such heterogeneous materials aslinear low density polyethylene (LLDPE), linear medium densitypolyethylene (LMDPE) and very low and ultra low density polyethylene(VLDPE and ULDPE); and homogeneous polymers such as metallocenecatalyzed polymers such as EXACT™ materials supplied by Exxon, AFFINITY™and ENGAGE™ materials supplied by Dow, LUFLEXEN™ materials supplied byBASF and TAFMER™ materials supplied by Mitsui Petrochemical Corporation.These materials generally Include copolymers of ethylene with one ormore comonomers selected from C4 to C10 α-olefins such as butene-1(i.e., 1-butene), hexene-1, octene-1, etc.

As used herein the term “ethylene-ethylenically unsaturated estercopolymer” refers to the copolymers of ethylene with one or more estercomonomers containing a vinyl group such as ethylenelvinyl acetatecopolymers, ethylenelethyl acrylate copolymers, ethylenelbutyl acrylatecopolymers, ethylenelmethyl acrylate, ethylenelme thyl methacrylatecopolymers.

As used herein, the phrase “modifled polymer”, as well as more specificphrases such as “modified ethylene vinyl acetate copolymer”, refer tosuch polymers having an acid or, preferably, an anhydride functionality,such as maleic or fumaric anhydride or acid, grafted thereon and/orcopolymerized therewith and/or blended therewith. Preferably, suchmodified polymers have the anhydride functionality grafted on orpolymerized therewith, as opposed to merely blended therewith.

As used herein, “PVDC” refers to a vinylidene chloride copolymer whereina major amount of the copolymer comprises vinylidene chloride and aminor amount of the copolymer comprises one or more unsaturated monomerscopolymerizable therewith, typically vinyl chloride, and alkyl acrylates(e.g. methyl acrylate) or to a blend thereof in different proportions.This term also includes the co-polymer(s) when blended with additives,such as stabilizers, plasticisers, etc., as known in the art.

As used herein, the phrase “directly adhered”, as applied to filmlayers, is defined as adhesion of the subject film layer to the objectfilm layer, without a tie layer, adhesive, or other layer therebetween.As used herein “contiguous”, when referred to two layers, is intended torefer to two layers that are directly adhered one to the other. Incontrast, as used herein, the word “between”, as applied to a film layerexpressed as being between two other specified layers, includes bothdirect adherence of the subject layer to the two other layers it isbetween, as well as lack of direct adherence to either or both of thetwo other layers the subject layer is between, i.e., one or moreadditional layers can be imposed between the subject layer and one ormore of the layers the subject layer is between.

As used herein, the phrases “inner layer” and “internal layer” refer toany film layer having both of its principal surfaces directly adhered toanother layer of the film.

As used herein, the phrase “outer layer” refers to any film layer havingonly one of its principal surfaces directly adhered to another layer ofthe film.

As used herein, the term “core”, and the phrase “core layer” refer toany internal film layer which has a primary function other than servingas an adhesive or compatibilizer for adhering two layers to one another.

As used herein, the phrase “bulk layer” refers to any layer which ispresent for the purpose of improving the abuse-resistance, toughness,modulus, etc., of the film. Bulk layers generally comprise polymerswhich are inexpensive relative to other polymers in the film whichprovide some specific purpose unrelated to abuse-resistance, modulus,etc.

As used herein, the phrase “tie layer” refers to any internal layerhaving the primary purpose of adhering two layers to one another.

DETAILED DESCRIPTION OF THE INVENTION

A first object of the present invention is a pillow pouch containing aflowable product characterized in that the packaging material is athermoplastic film comprising an RF sealable outer layer of EVAcontaining from about 14 to about 28 wt. % VA and a layer of PVDC.

As used herein the term “a layer of EVA” is used to mean that the basethermoplastic material of the layer is essentially EVA. In the EVA layerthe thermoplastic material may however contain the conventionalanti-block and slip agents, such as silica, either natural or syntheticsilica, calcium stearate, amides or bis-amides, etc., opacifying agents,e.g. CaCO₃, pigments, e.g. TiO₂, UV absorbers, etc. as known in the art.These additives can be added up to about 30 wt. %, preferably howeverthey are limited to a maximum of about 20%, and more preferably to amaximum of 15 wt. %, calculated on the weight of the RF-sealable outerlayer. Generally anti-block and slip agents are added to the sealinglayer in an amount up to about 10 wt. %, typically up to 8 wt. %, whilea higher amount of opacifying agents and pigments, up to about 20 wt. %,can be employed without problems. As used herein “essentially EVA” doesnot exclude the presence of minor proportions, e.g. up to less thanabout 10%, of other thermoplastic materials provided said materials donot impair the RF-sealability of said outer layer. Examples ofthermoplastic materials that might be present In minor proportions inthe outer RF-sealable layer of EVA are ethylenemethylacrylate,ethylene-ethylacrylate, ethylene-butylacrylate copolymers, PVDC, and thelike polar polymers. In a preferred embodiment however the basethermoplastic material of the EVA layer is only EVA.

Preferably, the thermoplastic film to be used in the manufacture ofpillow pouches according to the present invention, has a sealing layerof an ethylene-vinyl acetate copolymer containing at least 16 wt. % ofvinyl acetate. More preferably said ethylene-vinyl acetate copolymerwill contain from about 16 to about 22 wt % VA. While ethylene-vinylacetate copolymers with a VA content lower than 14 wt. % are hardlyRF-sealable, ethylene-vinyl acetate copolymers with more than 22 wt. %VA are RF sealable but they are generally very soft and sticky and maycreate some difficulties when used as the outer layers in a structure tobe run on a conventional VFFS machine.

When used in applications where high odor- and gas-barrier propertiesare required, the film will typically have an Oxygen Transmission Rate(OTR) lower than 50 cm³/m².d.atm, when measured at 23° C. and 0% or 100%of relative humidity, and a moisture vapour transmission rate (or MVTR)≦25 g/m².d when measured at 38° C. and 98% of relative humidity.

While the OTR is evaluated by following the method described in ASTMD-3985 and using an OX-TRAN instrument by Mocon, the MVTR is measured byASTM F-1249 using a Permatran W-1 instrument by Mocon.

This can be easily obtained using a PVDC with a low content ofplasticisers. In such a case, the thickness of PVDC can be as low as 3μm still providing for optimum gas- and odour-barrier properties, butpreferably it is at least 5 μm, and typically it is comprised betweenabout 5 and about 25 μm. These PVDC with a low content of plasticisersare those conventionally employed in the food packaging area to obtainhigh oxygen barrier properties.

On the other hand when used for packaging gas-emitting products the filmwill typically have an OTR of at least about 100 cm³/m².d.atm,preferably of at least 120 cm³/m².d.atm, and even more preferably of atleast 150 cm³/m².d.atm.

Such a high OTR can be obtained in a PVDC containing structure byreducing the thickness of PVDC andlor increasing the amount ofplasticisers blended therein. It is in fact widely known that the oxygenpermeability of PVDC increases with increasing plasticiser content

Additives that can satisfactorily be employed to increase the OTR of thePVDC layer comprise the plasticizers conventionally employed, in smallamounts, as processing aids for high-barrier PVDC, such as epoxycompounds, e.g. epoxidized linseed oil, epoxidized soybean oil, epoxyresins (such as for instance EPON 828 by Shell), alkyl esters, such asdibutyl sebacate, acetal tributyl citrate, phosphates, such as 2-ethylhexyl diphenyl phosphate (sold by Monsanto as Santicizer-141),phenoxypropylene oxide, EVA with a wt, % VA higher than 15 (such as theElvax™ resins by DuPont), modified EVA (such as the Elvaloy™ resins soldby DuPont), impact modifiers such as chlorinated polyethylene, butylrubber, chloro-butyl rubber, ethylene-propylene rubber (EPM),elastomeric terpolymer from ethylene, propylene and a conjugated diene(EPDM), polyisobutylene, styrene-butadiene copolymers, etc.

The amount of plasticizer(s) to be added to the PVDC resin depends onthe desired OTR and on the PVDC thickness in the overall structure.Generally, however, it becomes difficult to blend the PVDC resin withthe liquid plasticizer(s), such as the epoxidised linseed oil, theepoxidised soybean oil, the epoxy resins and the alkyl esters, when theamount thereof is higher than 16-20 wt. %. Typically therefore theamount of liquid plasticizer(s) in the PVDC blend will be up to about 15wt. %, preferably from about 1 wt. % up to about 10 wt. %, morepreferably from about 3 wt. % up to about 8 wt. %. Solid plasticizers,such as EVA, modified EVA, impact modifiers, e.g. those listed above,can be admixed to the PVDC up to about 50 wt. %, preferably up to about40 wt. % and more preferably up to about 30 wt. %. Solid and liquidplasticizers can also be employed in combination. In such a case thePVDC powder is first thoroughly blended with the solid plasticizer(s),in powder form, and then the liquid plasticizer(s) is blended thereto.

Other additives, such as stabilizers, UV absorbers, deodorizers,antioxidizers, etc. can be added to the PVDC resin. These otheradditives are generally used in minor amounts, typically up to about 2wt %.

To increase the film OTR the thickness of the PVDC can be reduced downto about 1 μm. Conventional thickness, e.g. 3, 5, 10 μm, or even more,may however provide the desired OTR depending on the amount and type ofplasticisers contained therein.

Preferably the film according to the invention has at least 3 layers,wherein the PVDC layer is a core layer and the other outer layer, thatmay be involved in the longitudinal sealing in case of lap seals, isalso of ethylene-vinyl acetate copolymer with from about 14 to about 28wt. % of VA.

Other layers may be present in the film such as tie layers or bulklayers. Suitable bulk layers will comprise ethylene-ethylenicallyunsaturated ester copolymers, preferably ethylene-vinyl acetatecopolymer, polyethylene homopolymers or ethylene-α-olefin copolymers,provided the RF sealability of the structure is maintained.

Suitable tie layers may comprise modified ethylene-vinyl acetatecopolymers or modified polyethylenes.

In a preferred embodiment the thermoplastic film to be used in themanufacture of pillow pouches according to the present invention willcomprise at least 5 layers with at least one core layer of PVDC, outerlayers of ethylene-vinyl acetate copolymers with from about 14 wt. % VA,preferably about 16 wt. % VA, to about 28 wt. % VA and Intermediate tielayers comprising optionally modified ethylene-vinyl acetate copolymers.

As indicated above, thermoplastic films 75-150 μm thick could replacePVC in the current VFFS machines and provide a better performance thanthe conventional 250 μm thick PVC film used in these machines. Thickerfilms can however be employed for highly demanding applications orthinner films for very small pouches. Generally, the thickness ofsuitable films may range from about 50 to about 250 μm, preferably itwill range from about 70 to about 200 μm, more preferably from about 75to about 150 μm.

The thickness of the sealing layer is generally at least 10 μm,preferably it is at least 20 μm, and even more preferably at least 30μm. As the polymer used for the sealing layer may also be used toprovide the desired thickness to the film, in some instances very thicksealing layers will be present, such as in the case of a 3-layerstructure.

The thermoplastic film suitable for use in the manufacture of pillowpouches according to the present invention is generally obtained bycoextrusion. The film is not stretched or oriented, at leastintentionally. A slight orientation, so-called accidental orientation,may be present depending on the production method employed.

A preferred method of manufacture thereof is the hot blown method.

Alternatively it is possible also to use the cast extrusion method,either through a round or preferably through a flat die. The castextrusion method also allows to obtain the film by extrusion coating.

In a most preferred embodiment the film will be obtained by the bubblecollapse technique that provides for collapsing the bubble obtained bythe hot blown method, when the resin inside is still hot, and pressingit so as to obtain a single web with a thickness twice that of theextruded film and an even number of layers with two separate PVDClayers. Said preferred film may for instance comprise 6, 8, or 10layers, preferably 6 or 10. To improve adhesion between the twoinnermost layers of the coextruded film of the bubble, preferably anethylene-vinyl acetate copolymer with a high content of VA is employed,such as an ethylene-vinyl acetate copolymer with from about 16 to about35 wt. % VA, preferably from about 18 to about 32 wt. % VA, morepreferably from about 22 to about 28 wt % VA.

The films obtained by this method are particularly suitable as PVCreplacement in the manufacture of pillow pouches. The presence of twoseparate PVDC layers further improves the desired balance betweenstiffness and flexibility, while the manufacturing cost is reducedbecause the ply separation step is avoided.

A second object of the present invention is therefore a symmetricalthermoplastic film with an even number of layers, outer layerscomprising an ethylene-vinyl acetate copolymer with from about 14 toabout 28 wt. % of VA and two PVDC inner layers, separated by at leasttwo contiguous layers comprising ethylene-vinyl acetate copolymer.

Preferably said symmetrical structure will have a thickness of at leastabout 50 μm, more preferably at least about 70 μm, and even morepreferably at least about 75 μm.

In a preferred embodiment at least two contiguous layers inbetween thetwo PVDC layers in said symmetrical structure comprise ethylene-vinylacetate copolymer with from about 16 to about 35 wt. % VA, preferablyfrom about 18 to about 32 wt. % VA, more preferably from about 22 toabout 28 wt. % VA.

Preferred symmetrical structures will comprise outer layers ofethylene-vinyl acetate copolymer with from about 14 to about 28 wt. % ofVA and two PVDC inner layers, separated by at least two contiguouslayers of ethylene-vinyl acetate copolymer with from about 22 to about28 wt. % VA.

A third object of the present invention is a symmetrical thermoplasticfilm with an even number of layers, outer layers comprising anethylene-vinyl acetate copolymer with from about 14 to about 28 wt. % ofVA and two PVDC inner layers, separated by at least two contiguouslayers comprising ethylene-vinyl acetate copolymer, whenever obtained bythe collapsed bubble process.

In the manufacture of pillow pouches with the thermoplastic materialaccording to the present invention, any VFFS machine can be used whichis equipped with an RF sealing equipment, such as for instance thosecommercially available from Thimmonier, or Sertic. In line of principlehowever any conventional VFFS machine can be adapted to the manufactureof RF-sealable pillow pouches by simply equipping it with a weldingapparatus such as those commercially available from e.g. Colpitt,Cosmos, or Kiefel.

While the longitudinal seal can be obtained either by a conventionalheat seal or by an RF seal, the transverse seal is always obtained by anRF seal. In the actual practice the RF seal is obtained by applying apressure to the two film webs to be welded together, e.g. by means of acouple of bars, and welding the two webs together by RF at a frequencyof about 27 MHz, which is the usual frequency provided in RF weldingapparatuses. The temperature of the bars can be varied from about roomtemperature to as high as possible as long as the film does not stickthereto. In line of principle it would be preferable to have heated barsas this would shorten the welding time. While with PVC the bars are keptat about room temperature because PVC starts sticking at temperaturesjust above room temperature, with the thermoplastic films according tothe present invention, having EVA outer layers, the temperature of saidbars can suitably be increased up to 70-80° C. The welding time is—asindicated above—function of the temperature of the bars, but also of thepressure applied, of the thickness of the film, etc. Typically weldingtime of from about 0.5 to about 3 seconds can be used and pressure up toabout 6 atm, preferably up to 5 atm. Optimal welding conditions canhowever be easily set by any skilled operator.

The film according to the present invention can however be employed inthe manufacture of pillow pouches in any type of machine that can beused to this purpose.

A fourth object of the present invention is a method of packaging aflowable product in a pillow pouch using an RF weldable filmcharacterized in that the RF weldable film is a multilayer thermoplasticfilm with an RF sealable outer layer of EVA containing from about 14 toabout 28 wt. % VA and a PVDC layer. In a preferred embodiment of thismethod of packaging, the flowable product is packaged in a pillow pouchby means of a VFFS machine.

The invention will now be described with reference to the followingexamples which are intended to be illustrative of some preferredembodiments of thermoplastic films particularly suitable for themanufacture of pillow pouches for packaging of flowable products.

Said examples should not be interpreted as a limitation to the scope ofthe present Invention.

Melt Flow Indexes (MFI's) are measured by ASTM D-1238, Condition E, 190°C./2.16 kg, and are reported in grams/10 minutes.

The densities have been measured by ASTM D 792.

Melting points, if not otherwise indicated, have been determined by DSCfollowing ASTM D-3418 (2^(nd) heating −10° C./min).

OTR is evaluated, at 23° C. and 0% or 100% R.H., according to ASTMD-3985 using an OX-TRAN instrument by Mocon.

MVTR is measured by ASTM F-1249 using a Permatran W-1 Instrument =byMocon.

EXAMPLE 1

A 3-layer film is obtained by hot blown having the following structure:A/B/A, wherein A is an ethylene-vinyl acetate copolymer with 18 wt % VA,MFI=0.7 g/10′, m.p.=87° C. (Elvax 3165 commercially available fromDuPont) comprising about 0.3% of silica and about 0.5% of erucamide, andis about 42 μm thick; B is a 3 μm-thick layer of PVDC (VDCGC) containingabout 7 wt. % of epoxidized soybean oil, about 1 wt. % of hydrotalciteand about 0.3 wt. % of a UV absorber.

EXAMPLE 2

A 5-layer film is obtained by hot blown having the following structure:A/C/B/C/A, wherein the resins employed for layers A and B and theadditives contained therein are as defined in Example 1 and C is anethylene-vinyl acetate copolymer with about 27 wt. % VA, MFI=4 g/10′, m.p.=72° C. (Evatane™ 2803 commercially available from Elf Atochem). Theoverall thickness of the structure was 75 μm, with a layer ratio of5/2/1/2/5.

EXAMPLE 3

A 5-layer film is obtained by hot blown having the following structure:A/C/B/C/A, wherein the resins employed for layers A and B and C and theadditives contained therein are as defined in Example 2. The overallthickness of the structure was 140 μm, with a layer ratio of 5/1/2/1/5.

EXAMPLE 4

A white and glossy 5-layer film having the following structure:A′/C/B/C/A wherein A, B, and C are as defined in Example 2 and A′corresponds to A with the addition of 6 wt. % of a masterbatch of whitepigment (60 wt. % TiO₂, 40 wt. % of carrier ethylene-vinyl acetatecopolymer), is obtained by hot blown.

EXAMPLE 5

A 10-layer film is obtained by coextruding a 5-layer film having thestructure A/C/B/C/C, wherein A, B, and C are as defined in Example 1 and2, by the hot blown method and then collapsing the tube during windingat the winding machine by means of collapsing pinch rolls. The finalfilm has the following structure: A/C/B/C/C/C/C/B/C/A, an overallthickness of 130 μm, and a layer ratio of 10/5/1/5/10/10/5/1/5/10.

OTR of this structure is 115 cm³/m².d.atm.

EXAMPLE 6

A 10-layer film having the structure A′/C/B/C/C/C/C/B/C/A′ is obtainedby following the procedure of Example 5 but replacing resin A with A′ asdefined in Example 4.

EXAMPLE 7

The procedure of Example 5 is repeated by replacing B with B′ which isPVDC (VDC-VC) comprising 10 wt. % of epoxidized soybean oil, 1 wt. % ofhydrotalcite, and 0.3 wt. % of a UV absorber. The end 10-layer film, 130μm thick, has the following structure A/C/B′/C/C/C/C/B′/C/A wherein thethickness ratio among the layers is as in Example 5.

OTR of this structure is 141 cm³/m².d.atm.

EXAMPLE 8

The procedure of Example 5 is repeated by replacing B with B″ which isPVDC (VDC-VC) comprising 4 wt. % of epoxidized soybean oil, 1 wt. % ofhydrotalcite, 0.3 wt. % of a UV absorber and about 5 wt. % of a modifiedEVA (Etvaloy™ 742, commercially available from DuPont) The end 10-layerfilm, 130 μm thick, has the following structure A/C/B″/C/C/C/C/B″/C/Awherein the thickness ratio among the layers is as in Example 5.

OTR of this structure is 199 cm³/m².d.atm.

EXAMPLE 9

The procedure of Example 5 is repeated by replacing B with B″ which isPVDC (VDC-VC) comprising 4 wt. % of epoxidized soybean oil, 1 wt. % ofhydrotalcite, 0.3 wt. % of a UV absorber and about 10 wt. % of amodified EVA (Elvaloy™ 742, commercially available from DuPont) The end10-layer film, 130 μm thick, has the following structureA/C/B′″/C/C/C/C/B′″/C/A wherein the thickness ratio among the layers isas in Example 5.

OTR of this structure is 394 cm³/m².d.atm.

EXAMPLE 10

A 5 layer film having the structure A/C′/B/C′/A has been obtained byfollowing the procedure of Example 2 but using C′, an anhydride-graftedpolyolefin in ethylene-vinyl acetate copolymer (Plexar™ 107 commerciallyavailable from Quantum), instead of resin C.

EXAMPLE 11

A 10-layer film having the structure A″/C/B/C/C/C/C/B/C/A″ is obtainedby following the procedure of Example 5 but replacing A with A″ which isa blend of A and 20 wt. % of a masterbatch comprising 40 wt. % of A asthe carrier and the remaining 60 wt. % of a mix of TiO₂, CaCO₃, silicaand erucamide. The thickness of the two combined PVDC layers is 8 μm,that of each of the two outer layers 40 μm, and the thickness of theoverall 10-layer film is 130 μm.

EXAMPLE 12

The procedure of Example 9 is repeated by increasing the amount ofmodified EVA from 10 wt. % to 25 wt. %.

OTR of this structure is about 1,000 cm³/m².d.atm.

EXAMPLE 13

A 7-layer film having the structure A/D/C′/B/C′/D/A wherein A, B, and C′are as defined in Examples 1 and 10, and D is an ethylene-octene-1copolymer with d=0.920, MFI 1 g/10′, and m.p. =124° C. (Dowlex™ 2045Ecommercially available from Dow), is obtained by the hot-blowntechnique. The overall thickness is 120 μm and the layer ratio is9/2/2/2/2/2/9.

EXAMPLE 14

A 10-layer film having the structure A″/C/B^(iv)/C/C/C/C/B^(iv)/C/A″ isobtained by following the procedure of Example 5 but replacing A with A″which is a blend of A and 20 wt. % of a masterbatch comprising 40 wt. %of A as the carrier and the remaining 60 wt. % of a mix of TiO₂, CaCO₃,silica and erucamide, and B with B^(iv) which is PVDC (VOC-VC)comprising 4 wt. % of epoxidised soybean oil, 1 wt. % of hydrotalcite,and 0.3 wt. % of a UV absorber. The thickness of the two combined PVDClayers is 20 μm, that of each of the two outer layers 30 μm, and thethickness of the overall 10-layer film 130 μm.

The OTR of the above structure at 0% and 100% R.H. is 13 and 14cm³/m².atm.day respectively.

MVTR of the above film at 38° C. and 98% R.H. was 4.7 g/m².

EXAMPLE 15

By following essentially the same procedure of the foregoing Example butvarying the thickness of the outer layers from 30 μm to 25 μm, and thatof the inner layers C to 5 μm each, a 10-layer 100 μm-thick film isobtained, with a layer ratio of 5/1/2/1/1/1/1/2/1/5.

EXAMPLE 16

By following essentially the same procedure of Example 14 but replacingA″ with A as in Example 1, a high barrier 10-layer film, 130 μ-thick, isobtained with the following structure A/C/B^(iv)C/C/C/C/B^(iv)/C/A.

EXAMPLE 17

The film of Example 14 (160 mm width) was used on a Thimmonier VFFSmachine for the manufacture of 250 cc pouches filled with a softener.Both the longitudinal seal (a lap seal about 8 mm wide) and thetransverse seals were made by an RF sealer operating at 27.12 MHz. Theline was running at about 45 pouches per minute. The seal resistance ofthe thus obtained pouches was evaluated by placing the pouch between twoparallel horizontal stainless steel plates and increasing the pressureapplied to the upper one until the pouch breaks. Said test was carriedout on the pouches 2 hours after their manufacture and the pouchesshowed to withstand the applied pressure up to 250 kg. The same test,repeated after storage of the pouches for 3 months at room temperature,shows no statistically significant difference thus confirming that,unlike with PVC, with the structures according to the present Inventionthere is no deterioration of the mechanical properties of the packagingmaterial with time. The appearance of the pouches after 3 month storageis almost identical to that of the original pouches.

PVC pillow pouches are actually employed for the packaging of flowable,generally liquid or pasty, non food products, such as products forpersonal hygiene such as soaps, shampoos, creams, lotions, etc. andhousehold products such as detergents, chemical solutions, etc. The useof PVC in the manufacture of pillow pouches for food products, becauseof the migration of plasticizers into the product, would in fact beunacceptable. On the contrary with the films described in the presentapplication, It Is possible to broaden up the range of products that canbe packaged by including also food products, such as cold or warmsauces, creams, soups, and the like products. High and medium gas- andodour barrier properties could be achieved by modifying the PVDClayer(s).

What is claimed is:
 1. A thermoplastic multi-layer film with an evennumber of layers comprising: a) first and second outermost layers A eachcomprising ethylene-vinyl acetate copolymer having between 14 and 22 wt.% vinyl acetate; b) first and second inner layers B each comprisingvinylidene chloride copolymer; and c) first and second contiguous layersC separating first and second inner layers B from each other, each layerC comprising ethylene-vinyl acetate copolymer.
 2. The thermoplastic filmof claim 1 which is between 50 and 250 μm thick.
 3. The thermoplasticfilm of claim 1 comprising first and second outer layers A eachcomprising ethylene-vinyl acetate copolymer having between 16 and 22 wt.% vinyl acetate, first and second inner layers B each comprisingvinylidene chloride copolymer; and first and second contiguous layers Cseparating first and second inner layers B from each other, each layer Ccomprising ethylene-vinyl acetate copolymer having between 16 and 32 wt.% vinyl acetate.
 4. The thermoplastic film of claim 3 wherein the firstand second inner layers B are separated from each other by at least twocontiguous layers C comprising ethylene-vinyl acetate copolymercontaining from 22 to 28 wt. % vinyl acetate.
 5. The film of claim 1wherein the film has the layer sequence A/B/C/C/B/A.
 6. The film ofclaim 1 wherein the thermoplastic multi-layer film is between 70 and 200μm thick.
 7. The film of claim 1 wherein the thermoplastic multi-layerfilm is between 75 and 150 μm thick.